Chlorinated rubbers (for example, chlorinated polyethylene rubbers and chlorosulfonated polyethylenes) have excellent properties such as resistance to thermal aging, oil resistance, cold resistance, weatherability, flame resistance, and electric properties, and they are used as the molding materials of various high pressure hoses as such as automobile power steering hoses; cable sheaths; gaskets; packings; and other molded articles.
Of such molding materials, the high pressure hoses produced by using a chlorinated rubber for the rubber layer should have sufficient resistance to degradation by zinc because, when such hoses become in contact with a metal part, and in particular, with zinc-plated joint at a high pressure and a high temperature, the chlorinated rubber constituting the rubber layer is rapidly and harshly degraded or hardened with cracks formation in the rubber layer or embrittlement or tearing of the rubber layer.
As a technique to solve such problems, patent document 1 discloses a composition for chlorinated polyethylene crosslinked rubber comprising (a) 100 parts by weight of chlorinated polyethylene, (b) 2 to 10 parts by weight of organic peroxide, (c) 3 to 20 parts by weight of crosslinking aid, and (d) 3 to 40 parts by weight of at least one acid acceptor selected from hydrotalcites and zeolites (claim 1).    Patent document 1: JP 2001-226546 A